Over the next 5 years, the main objective of this project will be to isolate and analyze visual system mutations in zebrafish. Mutations are induced in zebrafish by exposing males to ethylnitrosurea. Dominant mutations are looked for in Fl generation fish, whereas recessive mutations are isolated from F3 generation fish bred from F2 generation siblings. Both developmental and functional mutations will be sought, the latter by the use of visual behavioral tests developed in our laboratory. After mutants are isolated, they are characterized by light and electron microscopy, immunohistochemistry, in situ hybridization, electroretinography and mosaic analysis. A particular thrust of the next few years of the project will be to map mutated genes and, in certain cases, to clone and sequence the mutated genes. Another aspect of this research project is to study normal retinal development in zebrafish. The focus for the next several years will be on the role of retinoic acid in establishing the dorsal-ventral axis in the eye. To this end, we will examine the temporal and spatial expression patterns of retinoic acid synthetic and degrading enzymes in the zebrafish eye.